The invention relates to a chipboard wherein a lining or lamination adheres to the surface thereof by means of an adhesive substance. The present invention also relates to a method of laminating thin chipboards with sheet material using a press, the press having a heated roll and a belt, under tension, which partly loops about the roll. The belt arrangement is such that the thin chipboard and a sheet of non-thermoplastic material, preferably printed paper or textile fabric, positioned on the side of the chipboard nearest the roll, are guided into the gap which exists between the belt and the roll, and at the same time thermoplastic material is introduced between the non-thermoplastic sheet and the chipboard.
German published specification P 22 01 302 describes a press for laminating thin sheets to thin chipboards, characterized by a heated roll, means for the continuous introduction of a web of sheet material of thermoplastic type between the heated roll and the thin chipboard running on to the roll, and a belt, under tension, which is partly looped about the roll and which presses the thin chipboard and the sheet against the surface of the roll. The roll is maintained at a temperature at which the plastic material is brought to a plastic state, and, together with the sheet of thermoplastic material and the thin chipboard, a web of printed paper or textile fabric runs on to the heated roll on the side of the thermoplastic sheet remote from the chipboard. Laminating chipboards with printed paper with the use of thermoplastics as binder has the great advantage that heating of the thermoplastic sheet and of the chipboard is required only on the chipboard surface facing the thermoplastic sheet. This not only results in a saving in heat but more importantly obviates blistering, since the substantially vapor-impervious chipboard does not reach a temperature at which vapor could be formed which would tend to lift the generally vapor-impervious paper thus forming blisters. It is also proposed to apply a thermoplastic film on the side of the paper web remote from the chipboard to provide a watertight covering for the paper.
When using a press of this kind there is a disadvantage in that the heating of the thermoplastic sheet before passing it into the gap between roll and belt cannot be avoided, particularly because of heat radiation. Therefore, there is a risk that the thermoplastic sheet material may become plastic before it is taken up into the pressure gap. As a result, the thermoplastic sheet tears, primarily because the thermoplastic sheet is under tension to avoid distortion on running into the press gap.
A further disadvantage is that the paper of the binder shrinks to a considerable extent. When this occurs, the finished laminated board develops a curvature. Measures which may be taken to remove any such curvature run the risk of tearing the paper, particularly since not only the paper but also the wood in the chipboard is subjected to considerable modifications in length in accordance with its particular moisture content.
A further disadvantage of a board lamination in this way is that the surface is not weather-resistant.